WASHINGTON — Senators Tom Cotton and Ben Sasse have already been to Iowa this year, Gov. John Kasich is eyeing a return visit to New Hampshire, and Mike Pence’s schedule is so full of political events that Republicans joke that he is acting more like a second-term vice president hoping to clear the field than a No. 2 sworn in a little over six months ago.
President Trump’s first term is ostensibly just warming up, but luminaries in his own party have begun what amounts to a shadow campaign for 2020 — as if the current occupant of 1600 Pennsylvania Avenue weren’t involved.
The would-be candidates are cultivating some of the party’s most prominent donors, courting conservative interest groups and carefully enhancing their profiles. Mr. Trump has given no indication that he will decline to seek a second term.
But the sheer disarray surrounding this presidency, the intensifying investigation by the special counsel Robert S. Mueller III and the plain uncertainty about what Mr. Trump will do in the next week, let alone in the next election, have prompted Republican officeholders to take political steps that are unheard-of so soon into a new administration.
Asked about those Republicans who seem to be eyeing 2020, a White House spokeswoman, Lindsay Walter, fired a warning shot: “The president is as strong as he’s ever been in Iowa, and every potentially ambitious Republican knows that.”
But in interviews with more than 75 Republicans at every level of the party, elected officials, donors and strategists expressed widespread uncertainty about whether Mr. Trump would be on the ballot in 2020 and little doubt that others in the party are engaged in barely veiled contingency planning.
“They see weakness in this president,” said Senator John McCain, Republican of Arizona. “Look, it’s not a nice business we’re in."
Mr. Trump changed the rules of intraparty politics last year when he took down some of the leading lights of the Republican Party to seize the nomination. Now a handful of hopefuls are quietly discarding traditions that would have dictated, for instance, the respectful abstention from speaking at Republican dinners in the states that kick off the presidential nomination process.
In most cases, the shadow candidates and their operatives have signaled that they are preparing only in case Mr. Trump is not available in 2020. Most significant, multiple advisers to Mr. Pence have already intimated to party donors that he would plan to run if Mr. Trump did not.
Mr. Kasich has been more defiant: The Ohio governor, who ran unsuccessfully in 2016, has declined to rule out a 2020 campaign in multiple television interviews, and has indicated to associates that he may run again, even if Mr. Trump seeks another term.
Mr. Kasich, who was a sharp critic of the Republicans’ failed attempt to repeal the Affordable Care Act with deep Medicaid cuts, intends to step up his advocacy by convening a series of policy forums, in Ohio and around the country.
“He’ll continue to speak out and lead on health care and on national security issues, trade policy, economic expansion and poverty,” John Weaver, a political adviser of Mr. Kasich’s, said.
In the wider world of conservative Trump opponents, William Kristol, editor at large of The Weekly Standard, said he had begun informal conversations about creating a “Committee Not to Renominate the President.”
“We need to take one shot at liberating the Republican Party from Trump, and conservatism from Trumpism,” Mr. Kristol said.
It may get worse, said Jay Bergman, an Illinois petroleum executive and a leading Republican donor. Grievous setbacks in the midterm elections of 2018 could bolster challengers in the party.
“If the Republicans have lost a lot of seats in the Congress and they blame Trump for it, then there are going to be people who emerge who are political opportunists,” Mr. Bergman said.
Mr. Pence has been the pacesetter. Though it is customary for vice presidents to keep a full political calendar, he has gone a step further, creating an independent power base, cementing his status as Mr. Trump’s heir apparent and promoting himself as the main conduit between the Republican donor class and the administration.
The vice president created his own political fund-raising committee, Great America Committee, shrugging off warnings from some high-profile Republicans that it would create speculation about his intentions. The group, set up with help from Jack Oliver, a former fund-raiser for George W. Bush, has overshadowed Mr. Trump’s own primary outside political group, America First Action, even raising more in disclosed donations.
Mr. Pence also installed Nick Ayers, a sharp-elbowed political operative, as his new chief of staff last month — a striking departure from vice presidents’ long history of elevating a government veteran to be their top staff member. Mr. Ayers had worked on many campaigns but never in the federal government.
Some in the party’s establishment wing are remarkably open about their wish that Mr. Pence would be the Republican standard-bearer in 2020, Representative Charlie Dent of Pennsylvania said.
“For some, it is for ideological reasons, and for others it is for stylistic reasons,” Mr. Dent said, complaining of the “exhausting” amount of “instability, chaos and dysfunction” surrounding Mr. Trump.
Mr. Pence has made no overt efforts to separate himself from the beleaguered president. He has kept up his relentless public praise and even in private is careful to bow to the president.
Mr. Pence’s aides, however, have been less restrained in private, according to two people briefed on the conversations. In a June meeting with Al Hubbard, an Indiana Republican who was a top economic official in Mr. Bush’s White House, an aide to the vice president, Marty Obst, said that they wanted to be prepared to run in case there was an opening in 2020 and that Mr. Pence would need Mr. Hubbard’s help, according to a Republican briefed on the meeting. Reached on the phone, Mr. Hubbard declined to comment.
Mr. Ayers has signaled to multiple major Republican donors that Mr. Pence wants to be ready.
Mr. Obst denied that he and Mr. Ayers had made any private insinuations and called suggestions that the vice president wass positioning himself for 2020 “beyond ridiculous.”
For his part, Mr. Pence is methodically establishing his own identity and bestowing personal touches on people who could pay dividends in the future. He not only spoke in June at one of the most important yearly events for Iowa Republicans, Senator Joni Ernst’s pig roast, but he also held a separate, more intimate gathering for donors afterward.
When he arrived in Des Moines on Air Force Two, Mr. Pence was greeted by an Iowan who had complained about his experience with the Affordable Care Act — and who happened to be a member of the state Republican central committee.
The vice president has also turned his residence at the Naval Observatory into a hub for relationship building. In June, he opened the mansion to social conservative activists like Tony Perkins of the Family Research Council and representatives of the billionaire kingmakers Charles G. and David H. Koch.
At large gatherings for contributors, Mr. Pence keeps a chair free at each table so he can work his way around the room. At smaller events for some of the party’s biggest donors, he lays on the charm. Last month, Mr. Pence hosted the Kentucky coal barons Kelly and Joe Craft, along with the University of Kentucky men’s basketball coach, John Calipari, for a dinner a few hours after Ms. Craft appeared before the Senate for her hearing as nominee to become ambassador to Canada.
Other Republicans eyeing the White House have taken note.
“They see him moving around, having big donors at the house for dinner,” said Charles R. Black Jr., a veteran of Republican presidential politics. “And they’ve got to try to keep up.”
Mr. Cotton, for example, is planning a two-day, $5,000-per-person fund-raiser in New York next month, ostensibly for Senate Republicans (and his own eventual re-election campaign). The gathering will include a dinner and a series of events at the Harvard Club, featuring figures well known in hawkish foreign policy circles such as Stephen Hadley, Mr. Bush’s national security adviser.
Mr. Cotton, 40, a first-term Arkansas senator, made headlines for going to Iowa last year during the campaign. He was back just after the election for a birthday party in Des Moines for former Gov. Terry E. Branstad and returned in May to give the keynote speech at a county Republican dinner in Council Bluffs.
Mr. Sasse, among the sharpest Senate Republican critics of Mr. Trump, has quietly introduced himself to political donors in language that several Republicans have found highly suggestive, describing himself as an independent-minded conservative who happens to caucus with Republicans in the Senate. Advisers to Mr. Sasse, of Nebraska, have discussed creating an advocacy group to help promote his agenda nationally.
He held a private meet-and-greet last month with local Republican leaders in Iowa, where he lamented the plodding pace of Capitol Hill and declined to recant his past criticism of Mr. Trump.
Jennifer Horn, a former chairwoman of the New Hampshire Republican Party who hosted Mr. Sasse in the first primary state last year, said she saw the senator as speaking for conservatives who felt that Republicans in Washington had not been delivering on their promises.
“There are a lot of people in New Hampshire who have developed a lot of respect for him, and I’m one of them,” she said.
James Wegmann, a spokesman for Mr. Sasse, said the only future date that Mr. Sasse had in mind was Nov. 24, 2017, when the University of Iowa meets the University of Nebraska on the football field.
“Huskers-Hawkeyes rematch,” Mr. Wegmann said, “and like every Nebraskan, he’s betting on the side of righteousness.”
Beyond Washington, other up-and-coming Republicans are making moves should there be an opening in 2020. Nikki Haley, the ambassador to the United Nations and a former governor of South Carolina, put her longtime pollster on the payroll, has gotten better acquainted with some of New York’s financiers and carved out a far more muscular foreign policy niche than Mr. Trump.
“She sounds more like me than Trump,” said Senator Lindsey Graham, a hawkish Republican from South Carolina.